The production of gaseous oxygen by the cryogenic rectification of feed air requires the provision of a significant amount of refrigeration to drive the separation. Generally such refrigeration is provided by the turboexpansion of a process stream, such as a portion of the feed air. While this conventional practice is effective, it is limiting because an increase in the amount of refrigeration inherently affects the operation of the overall process. It is therefore desirable to have a cryogenic air separation process wherein the provision of the requisite refrigeration is independent of the flow of process streams for the system.
The refrigeration problem is more acute when the product gaseous oxygen is desired at an elevated pressure because generally in such a situation the oxygen is taken from the column system as liquid, pumped to a higher pressure, and then vaporized to produce the elevated pressure product. The removal of liquid oxygen from the column system increases the amount of refrigeration which must be delivered to the column system to drive the separation.
One method for providing refrigeration for a cryogenic air separation system which is independent of the flow of internal system process streams is to provide the requisite refrigeration in the form of exogenous cryogenic liquid brought into the system. Unfortunately such a procedure is very costly.
Accordingly it is an object of this invention to provide an improved cryogenic air separation process for the production of elevated pressure gaseous oxygen wherein the provision of the requisite refrigeration for the separation is independent of the flow of process streams.
It is another object of this invention to provide a cryogenic air separation process for the production of elevated pressure gaseous oxygen wherein the provision of the requisite refrigeration for the separation is independently and efficiently provided to the system.